Mubadala is Emirati, not Saudi. From the article, it seems that just the Vision Fund run by Mubadala has the backing of the Saudis
Saudi Arabia's "Public Investment Fund was established in 1971 to provide financing support for projects of strategic significance to the national economy" [2]. It is the Saudi analog to Abu Dhabi's Mubadala. PIF is an LP in the SoftBank Vision Fund, albeit a significant and likely influential one.
[1] https://en.m.wikipedia.org/wiki/Mubadala_Development_Company
[2] http://www.softbank.jp/en/corp/news/press/sb/2016/20161014_0...